The present invention relates to a method for processing biological material of various forms and origins by means of laser pulses which are generated with a laser system consisting of a pumping laser and a dye laser and which are focussed in a microscope to the theoretically possible limit.
It is known that laser light, in particular that from dye lasers, has a very low beam divergence and can therefore be very well focussed. To achieve this, it is in principle sufficient to image the laser beam in a focal plane through a lens or a system of lenses. In the case of the application of lenses of long focal length, a focus is obtained which is not very well defined in terms of its depth (in the direction of propagation of the light). It is however possible, by feeding the light into a microscope, to make use of the very short focal length of the microscope objective in order to generate a focal spot which has a small depth and the cross-section of which corresponds to the wavelength of the light.
A device of the type mentioned above is known from Science 213 (1981), pages 505 to 513, wherein an Nd-YAG laser pumps a dye laser, the pulses from which are fed into a microscope. At pulse lengths of 15 ns, this system was tuneable in the range from 217 to 800 nm. On the assumption of a rectangular pulse shape with time, the indicated peak power levels of 10.sup.5 W give a calculated pulse energy of 1.5 mJ; because of the irregular pulse shape typical in the case of lasers of this type, the pulse energy might actually have been from 0.5 to 0.7 mJ. The known device could be operated not only with tuneable pulses 15 ns in length but at three fixed wavelengths--266, 532 and 1064 nm--also with picosecond pulses (25 ps).
This device was employed to produce point lesions in chromosomes, subcellular organelles and nerve cells. From the deficits caused thereby, conclusions were drawn as to the function of the irradiated parts.